#include <iostream>
#include <queue>
#include <map>
#include <unordered_map>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>
#include <cstring>
#include <set>
#include <unordered_set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
const int INF=0x3f3f3f3f;
int main()
{
	ll a,b;
	ll n;
	cin>>a>>b>>n;
	ll w=a*5+b*2;
	ll num=n/w;
	ll d=num*7;
	n=n%w;
	int i=1;
	while(n>0)
	{
		if(i<=5)
		{
			n-=a;
		}
		else
		{
			n-=b;
		}
		d++;
		i++;
	}
	cout<<d;

	return 0;
}

